10.9: Electric Current
Electric Current Electric Current is the flow of electrons it is a measure of the rate of electron flow past a given point in a circuit measured in amperes (A)
Think of it in terms of a waterfall. If you could count the number of water molecules that drop over the edge every second, you could get the rate at which water is flowing past a particular point. Now think of the water molecules as electrons in a wire running past a particular point in a specific amount of time and you have the concept of current. Electric Current
Direct Current (DC) flows in only one direction (electrons from a battery) Alternating Current (AC) flows back and forth at regular intervals (comes from generators and carried to your home through power lines) Electric Current – two types
DC Direct Current AC Alternating Current
Current can KILL !
Measuring Current Current in a circuit is measured using an ammeter. The unit of electric current is the ampere (A). An ampere is a measure of the amount of charge moving past a point in the circuit every second.
Measuring Current A current of 1 ampere means that 6.2 x electrons pass a particular point every second.
Ammeter There are two terminals on the ammeter The negative (–) terminal is often black, The positive (+) terminal is often red.
Ammeter Always connect the positive terminal of the meter closest to the positive terminal of the electrical source (battery). Connect the negative terminal of the meter closest to the negative terminal of the electrical source.
Measuring Current Activity Fill in the following table as you follow the steps below Connection of AmmeterElectric Current (A) Between light bulb and switch Between battery and light bulb Between battery and switch Construct a circuit using a battery, light bulb, switch, and wires Connect the ammeter between the light bulb and switch Close the switch and note the current in the table Repeat the previous three steps after changing the position of the ammeter, as described in the table
Follow-up Does the current reading change if the ammeter is moved to a different position in the circuit? No! As long as the switch is closed, the current should be consistent throughout the circuit.
Homework Read pg Answer # 1 – 6 on pg. 315